JPS60227112A - Optical displacement meter - Google Patents

Abstract

PURPOSE:To enable detection of the change in the angle between a material to be measured and projecting optical axis and the change in the surface condition, material quality and color of the material to be measured while controling the quantity of the light detected by a PSD to specified quantity by outputting the driving level signal for a light source in addition to the result of the measurement of displacement. CONSTITUTION:A control circuit 30 for the output of the light source outputs the driving level signal 33 for the light source which subjects the output of the light source to feedback control to a circuit 1 for driving the light source and an output circuit 31 so as to maintain the specified level signal of the quantity of the light detected by a semiconductor position detecting element PSD8. The quantity of the light detected by the PSD8 is maintained constant by such feedback control and the quantity of said light is so controlled that the accuracy of calculation is not fluctuated by the change in the kind and surface condition of the material 5 to be measured, the distance between the optical system and the material 5 and the solid angle between the projecting optical axis 4 and the material 5. On the other hand the signal 33 is the controlled variable to be outputted so as to negate the fluctuation in the quantity of the light detected by the PSD8 with a change in each state and therefore the change in each state is known by outputting the signal 33.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical displacement meter that measures the shape of an object in a non-contact manner.

[Prior art]

A conventional device of this type is shown in FIG. In FIG. 1, 1 is a light source driving circuit, 2 is a semiconductor laser as a light source, 3 is a light projecting lens that condenses and irradiates the light of the semiconductor laser 2, and 4 is a light projecting optical axis of the light projecting lens 3. , 5 is an object to be measured, 6 is a light spot projected onto the object to be measured 5, 7 is a light-receiving lens that forms an image of the scattered light from the light spot 6 on a light-receiving element, and 8 is a semiconductor as a light-receiving element. Position detection element (hereinafter abbreviated as PSD) 9 a, 9
b is a preamplifier, lQa, 10b is a postamplifier, 1
1a.

11b is a rectifier circuit, 12a is an output signal V3, 12b is an output signal vb, 13 is a subtraction circuit, 14 is an addition circuit, 15 is a subtraction output signal va-vb, 16 is an addition output signal v;l+
vb, 17 is a division circuit, 18 is a division output signal (V8-
Vb)/(Va+vb), 19 is an A/D converter, 20
is the measurement result signal of the digitized displacement measurement result, 21
is the output control circuit of the light source.

Next, the operation will be explained. In FIG. 1, light output from a semiconductor laser 2 driven by a light source drive circuit 1 is focused by a projection lens 3 and projects a light spot 6 onto an object 5 to be measured. Semiconductor laser 2. Light projection lens 3
．． The optical system consisting of the light receiving lens 1 and PSD 8 is
It is arranged so that the distance from the light projection lens 3 to the light spot 6 can be measured by detecting the position of the received light image of the original spot 6 formed on the PSDB using the principle of triangulation. . In this case, the position
0b converts and amplifies the voltage, and rectifier circuits 11a, 11
When rectified by b, a pair of voltage signals va (12a') and Wb (12b) are given by the following equation.

However, n: distance from the center to the edge of the PSD 8, known value
Based on the predetermined arrangement of the optical system, the distance from the two signals va (12a) and Vb (12b) is determined by the subtraction circuit 13 and the addition circuit 14, respectively, as a subtraction signal (va-vb) 15 and an addition signal ( va+Vb)1
6, the division circuit 17 calculates (va-vb)AVa + vb)
By performing the division, the division output signal 18 which is the output of the division circuit 17 is obtained. Finally, this divided output signal 18 is digitized by an A/D converter 19 to obtain a displacement output signal 20 which is the displacement measurement result. In addition, the PSD 8 which is a light receiving element caused by the type of the object to be measured 5 - surface condition, color and change in distance between the optical system and the object to be measured 5, etc.
The output control circuit 21 of the light source controls the output of the semiconductor laser 2 so that changes in the amount of light incident on the PsD 8 do not affect the calculation accuracy of displacement, and the amount of light received by the PsD 8 is generally kept constant. has been done.

Conventional optical displacement meters are configured as described above, so in addition to the amount of displacement, changes in the solid angle formed by the surface to be measured and the light projection axis of the optical displacement meter, as well as the surface condition, material, and The drawback was that it was not possible to detect changes in color.

[Summary of the invention]

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional method.In addition to the displacement measurement value, the output amount of the feedback circuit for controlling the amount of light received by the light receiving element to be constant. By controlling this, it is possible to detect changes in the solid angle between the surface to be measured and the light emitting axis of the optical displacement meter, as well as changes in the surface condition, material, and color of the object to be measured, while maintaining a constant displacement measurement accuracy. Another object of the present invention is to provide an optical displacement meter that can detect changes in the displacement measurement state before displacement measurement accuracy is maintained or displacement measurement becomes impossible.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In FIG. 2, parts that are the same as or corresponding to those shown in the figure are given the same reference numerals. 22a and 22b are AC amplifier circuits, 23 is a signal switcher, 24 is a sample and hold circuit, and 25 is an A/
D converter, 26 is an arithmetic processor, 2γ is an arithmetic value signal output from the arithmetic processor 26, 28 is a timing pulse generation circuit, 29 is a received light amount detection circuit, 3o is a light source output control circuit, 31 is an output circuit, 32 is a received light amount level signal, 33 is a light source drive level signal, 34 is a lighting timing pulse signal for the semiconductor laser 20 as a light source, 35
is a signal switch control pulse signal of the signal switch 23, 36 is a sample hold control pulse signal of the sample hold circuit 24, 3T is an A/D converter control pulse signal of the A/D converter 25, and 38 is a signal switch control pulse signal of the arithmetic processor 26. 39 is an output circuit control pulse signal for the output circuit 31; 40 is a received light amount determining circuit; 41 is a determination data signal; 42 is an output timing pulse signal; 43 is a measurement result signal indicating the measurement result.

FIG. 3 is an example of a signal waveform diagram and a signal schematic diagram of the output timing pulse signal 42 and the measurement result signal 43, respectively. In FIG. 4, reference numeral 44 denotes an optical displacement meter, and 45 denotes a surface of the object to be measured 50, which has different light scattering characteristics than the others and reduces the amount of scattered light incident on the PSD 8 of the optical displacement meter, for example, a blackish color. This is the part. In FIG. 5, 44 is an optical displacement meter, and 48 is the distance between the optical displacement meter 44 and the object to be measured 5! It is.

Note that 46 and 47 are signal waveform diagrams of a measurement data signal indicating measurement data of the optical displacement meter and a displacement data signal indicating displacement data, respectively, which constitute the measurement result signal.

Next, the operation will be explained. Figure 2. First, let's talk about how to measure displacement. Lighting timing pulse signal 3
The light emitted from the semiconductor laser 2, which is turned on in synchronization with 4, passes through the projection lens 3 and is projected onto the object to be measured 5 as a light spot 6, and a part of the scattered light is transmitted through the reception lens 7 onto the PSO 8. A pair of current signals outputted from the PSD 8 are voltage-converted and amplified by preamplifiers 9a and 9bK, and further AC amplified by AC amplifiers 22a and 22b to form a pair of signals V. , vd. These two signals VC and Vd are sent to the signal switch 23. sample hold 2
4. The A/D converter 25 and the arithmetic processor 26 determine the respective peak-to-peak values Ve and V4, and calculate (ve vr)/(ve + vf).

By performing the calculation by the arithmetic processor 26, the distance to the light spot 6 on the object to be measured 5 is measured. Next, the received light amount detection circuit 29 receives the 2 signal V. , the sum of Vd is PSD8
Since the amount of received light is proportional to the amount of received light, the amount of received light of PSD8 is detected by calculating vo+vd, and the amount of received light level signal 3 is detected.
2 is output to the light source output control circuit 30 and the output circuit 31. The light source output control circuit 30 outputs a light source drive level signal 33 for applying light source amount feedback control to the light source drive circuit 1 and the output circuit 31 so that the received light amount level signal 32 of the PSD 8 is constant. By this feedback control, the amount of light received by psl)H is kept constant, and the calculation accuracy is adjusted based on the type, surface condition, color of the object to be measured 5, the distance between the optical system and the object to be measured, and the distance between the light projection axis 4 and the object to be measured. It is controlled to 5 so that it does not fluctuate due to changes in the solid angle formed by 5. On the other hand, the light source drive level signal 33 is the PSD due to each state change described above.
Since this is a control amount that is output so as to cancel out the fluctuation in the amount of received light of 8, by outputting this light source drive level signal 33, it is possible to know each of the above-mentioned state changes. The output circuit 31 outputs a displacement calculation value signal 27.degree. discrimination data signal 41. Received light amount level signal 32 and light source drive level signal 3
By synchronizing 3 with the output timing pulse signal 42 and outputting the measurement result signal 43, it is possible to obtain measurement information that could not be obtained conventionally for the measurement result of one displacement, and the measurement status can be understood. . For example, as shown in Figure 4, K
, when measuring the shape of the object to be measured 5, the displacement data signal 4
If there is a change in the scattered light characteristics on the surface to be measured even in a portion where no change occurs in the measurement data signal 46, the degree of the change can be measured using the measurement data signal 46. Also, as shown in Figure 5,
Even when measuring a slope, changes in the slope of the object to be measured 5 can be detected using the calculated data signal 46.

In the above embodiment, the light source output control circuit 30 outputs the light source drive level signal 33 to the output circuit 31, but the light source drive level signal 33 itself is not directly outputted, and the semiconductor laser Even if the current flowing through the circuit 2 is detected and outputted from the output circuit 311C, the same effect as in the above embodiment can be obtained. Although the output circuit 31 is used in the above embodiment, the calculated value signal 27. Received light level signal 32. The light source drive level signal 33 and the discrimination data signal 41 may be output directly.

〔Effect of the invention〕

As described above, according to the present invention, by outputting the light source drive L novel signal 33 in addition to the displacement measurement result, the change in the solid angle formed between the object to be measured 5 and the light projection axis -4 and the object to be measured are It is possible to detect changes in the surface condition, material, and color of the object 50 while controlling the amount of light received by the PSNS to a constant level, and also to detect changes in the surface condition, material, and color of the object 50.
2 are output together, so there is an effect that an optical displacement meter can be obtained which can perform measurement by arbitrarily determining the measurement limit, if necessary, even if the amount of light incident on the PSD 8 cannot be kept constant.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional optical displacement meter, FIG. 2 is a block diagram showing an optical displacement meter according to an embodiment of the present invention, and FIG. 3 is an explanatory diagram of output data according to an embodiment of the present invention.
FIG. 4 and FIG. 5 are explanatory diagrams of measurement examples. 1... Light source drive circuit, 2... Semiconductor laser, 3...
... Light emitting lens, 4... Light emitting optical axis, 5... Measured object, 6... Source spot, 7... Light receiving lens, 8...
Semiconductor device detection element (PSD), 9a, 9b-preamplifier, 22a, 22b... AC amplifier, 23...
・Signal switcher, 24...Sample hold circuit, 25
...A/D converter, 26 PA/arithmetic processor, 27
... Calculated value signal, 28... Timing pulse generation circuit, 29... Received light amount detection circuit, 30... Light source output control circuit, 31... Output circuit, 32... Received light amount level signal, 33... Light source drive level signal, 34... Lighting timing pulse signal, 35... Signal switch control pulse signal, 36... Sample hold control pulse signal,
37... A/D converter control pulse signal, 38... Arithmetic processor control pulse signal, 39... Output circuit control pulse signal, 40... Received light amount determination circuit, 41...
Discrimination data signal, 42... Output timing pulse signal, 43... Measurement result signal. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent applicant Mitsubishi Electric Corporation

Claims (1)

[Claims] An optical system arranged to measure the distance to an object to be measured using the principle of triangulation, a drive circuit for a light source that drives a semiconductor laser as a light source of the optical system, and a position of the object to be measured. an AC amplifier that amplifies a position detection signal of the semiconductor device detection element, a signal switcher that switches the output signal of the AC amplifier and inputs it to a sample and hold circuit, and the sample and hold circuit. an arithmetic processor that performs A/D conversion on the output of the digitized signal using an A/D converter and performs arithmetic processing on the digitized signal; the arithmetic processor, a light source drive circuit, a signal switch, a sample hold circuit, and an A/D conversion a timing pulse generation main circuit for supplying a pressure control pulse, and a light reception level signal to a light source output control circuit that receives the output signal of the AC amplifier and sends a light source drive level signal to the light source drive circuit; a received light amount detection circuit that sends out a received light amount detection circuit, a received light amount determination circuit that inputs the received light level signal and sends out a determination data signal, a calculated value signal of the arithmetic processor, the control nolus, the received light amount level signal, and the determined data. An optical displacement meter comprising an output circuit that inputs a signal and the drive level signal and sends out an output timing pulse signal and a measurement result output.